Staples have been used in general surgery for many years, mainly for anastomosing tissue. Examples include skin staplers used to close a skin incision in place of the standard manual suturing process, and end-to-end and end-to-side bowel stapling instruments which are generally one shot devices used during bowel reconstruction procedures.
The staples used with these devices are generally manufactured from a metal or metal alloy material such as stainless steel or titanium. The majority are constructed from round profile wire and generally produced in a generally ‘U’-shaped configuration. The ends of the ‘U’-shape are normally pointed or sharpened so as to ensure easy tissue penetration. Examples of prior art in this area include U.S. Pat. Nos. 4,505,273, 5,026,390 and 4,719,917.
In clinical use the staples are delivered using a stapler device which generally consists of an anvil component positioned inside the ‘U’ between staple legs and in contact with the staple. A former component is positioned on the other side of the staple base, the gap between the forming arms of the former being approximately the width of the anvil plus two times the diameter of the staple wire. The head of the stapler device is normally positioned centrally across the slit or opening which is to be closed.
On activation of the device the staple legs are advanced forward so that they penetrate the tissue on both sides of the slit or opening. As the former is advanced further the legs of the staple bend around the anvil causing the tips of the legs to advance along an arcuate path toward each other so that the staple ultimately assumes a generally rectangular shape thereby compressing the tissue which has been trapped between the staple legs. This compression of tissue is the mechanism by which a closure is effected. Depending on the length of the incision or opening a series of staples will be delivered along its length in order to ensure a blood tight closure.
While this method of closing an incision is effective when a series of staples are used along the length of the incision it is less effective when it is desirable to close the opening with the minimum number of staples. For example for an incision of 5-6 mm in length one round wire staple positioned centrally along the incision is insufficient to effect a closure as the compression due to the staple legs only acts in a limited area towards the center of the incision, leaving the extremities open.
Also in situations where the tissue is soft and friable the narrow staple leg will have a tendency to tear through the tissue as they are bent around the anvil thereby decreasing the level of compression between the staple legs and causing unnecessary damage to the vessel wall.
In order to avoid complications such as clot formation, it is important to retain the staple legs within the vessel wall, i.e. avoid the penetration of the internal wall on the introduction of a foreign body into the lumen of the vessel. If the staple legs penetrate into the lumen of the vessel there is the added danger that excessive pressure from the staple gun may cause the vessel to collapse, which can lead to the legs penetrating the opposing vessel wall, i.e. stapling the vessel walls together and blocking the lumen of the vessel.
Therefore there is a need for an improved surgical staple which will more effectively close an incision, thereby requiring fewer staples to close an incision. In addition it would be advantageous to profile the staple legs so that they are less inclined to tear through softer tissue. Furthermore, it would be desirable to limit the depth of penetration of the staple legs to prevent the legs entering the lumen of the vessel.